Percutaneous lead introducer

ABSTRACT

In general, the invention is directed to a technique for percutaneously introducing a stimulation lead into a target stimulation site via the epidural region proximate the spine of a patient. The process of introducing the stimulation lead may include the use of a hollow stimulation lead introducer, which comprises an elongated sheath and an elongated dilator. The dilator fits within the sheath and serves to widen a path through the epidural region for the introduction of a stimulation lead. At least a portion of the stimulation lead introducer has an oblong cross-section, allowing passage of stimulation leads such as paddle leads. The stimulation lead introducer may enter the epidural region proximate a spine of a patient via a guidewire. The stimulation lead introducer provides a path through the epidural region of a patient to a target stimulation site. A stimulation lead may travel through the path to reach the target stimulation site where it may provide therapy to the patient.

This application is a continuation of U.S. utility application Ser. No.11/823,521, filed Jun. 28, 2007, which is a continuation of U.S. utilityapplication Ser. No. 10/773,121, filed Feb. 5, 2004 and issued as U.S.Pat. No. 8,340,779, which is a continuation-in-part of U.S. utilityapplication Ser. No. 10/718,038, filed Nov. 20, 2003, which claims thebenefit of U.S. provisional application No. 60/499,207, filed Aug. 29,2003, the entire content of each of which is incorporated by referenceherein.

TECHNICAL FIELD

The invention relates to neurostimulation systems and, moreparticularly, to stimulation lead introducers.

BACKGROUND

Neurostimulation systems may be used to deliver neurostimulation therapyto patients to treat a variety of symptoms or conditions such as chronicpain, tremor, Parkinson's disease, multiple sclerosis, spinal cordinjury, cerebral palsy, amyotrophic lateral sclerosis, dystonia,torticollis, epilepsy, incontinence, or gastroparesis. Aneurostimulation system delivers neurostimulation therapy in the form ofelectrical pulses. In general, neurostimulation systems deliverneurostimulation therapy via electrodes on stimulation leads locatedproximate to the spinal cord, pelvic nerves, or stomach, or within thebrain of a patient.

The stimulation leads may include percutaneously implanted leads orsurgically implanted leads. Surgically implanted leads are often largerand wider than traditional percutaneously implanted leads. For example,surgically implanted leads may include paddle-shaped leads with surfaceelectrodes. Surgically implanted leads are often desirable because theyare less susceptible to migration, include unidirectional electrodearrays, and provide reduced power consumption. Although surgical leadscan provide more effective leads, percutaneously implanted leads areoften preferred because they are implanted in a less invasive manner.

SUMMARY

In general, the invention is directed to techniques for percutaneouslyintroducing a generally flat stimulation lead into a target stimulationsite via the epidural region proximate the spine of a patient. A numberof electrodes on the stimulation lead, which may be a paddle-like lead,rest at a target stimulation site where the electrodes can providestimulation therapy to the patient.

The process of introducing the stimulation lead includes the use of ahollow stimulation lead introducer, which comprises an elongated sheathand an elongated dilator. The dilator fits within the sheath and servesto widen a path through the epidural region for the introduction of thesheath, and ultimately the stimulation lead. At least a portion of thestimulation lead introducer has an oblong cross-section, allowingpassage of flat stimulation leads such as paddle leads.

The stimulation lead introducer may enter the epidural region proximatethe spine of a patient via a guidewire. The stimulation lead introducerprovides a path through the epidural region of a patient to a targetstimulation site. The stimulation lead travels along the path defined bythe lead introducer to reach the target stimulation site where it ispositioned to deliver therapy to the patient.

In one embodiment, the invention is directed to a stimulation leadintroducer comprising an elongated dilator defining a dilator lumensized to advance over a guidewire, the dilator having a substantiallyconical distal tip, wherein at least a portion of the conical distal tiphas a substantially oblong cross-section, and an elongated sheathdefining a sheath lumen sized to accommodate the dilator or thestimulation lead.

In another embodiment, the invention is directed to a method forintroducing a stimulation lead comprising inserting a stimulation leadintroducer into an epidural region proximate a spine of a patient via aguidewire, wherein the introducer includes an elongated dilator defininga dilator lumen sized to advance over the guidewire, the dilator havinga substantially conical distal tip, wherein at least a portion of theconical distal tip has a substantially oblong cross-section, and anelongated sheath defining a sheath lumen sized to accommodate thedilator or the stimulation lead, withdrawing the dilator from thesheath, and introducing a stimulation lead to a target site within theepidural region via the sheath.

In a further embodiment, the invention is directed to a dilator forwidening a path for a stimulation lead to travel through an epiduralregion proximate a spine of a patient, the dilator having a proximal endand a distal end, wherein the dilator defines a dilator lumen sized toadvance over a guidewire, the dilator having a substantially conicaldistal tip, wherein at least a portion of the conical distal tip has asubstantially oblong cross-section.

The invention may provide one or more advantages. For example, theinvention permits percutaneous introduction of leads that ordinarilyrequire surgical implantation. In particular, generally flat, or“paddle-like,” leads may be introduced into the epidural regionproximate a spine of a patient without the need for surgicalintervention. Instead, the dilator and sheath associated with theinvention permit introduction of flat leads by less invasive,percutaneous incision, reducing patient trauma and recovery time.

The invention may further provide more customizable components forintroducing the stimulation lead. In particular, at least one of thesheath and the dilator may include deformable material, such aspolyethylene. The deformable properties of the material allow thedilator to be formed to fit the anatomy of a patient more precisely. Inaddition, the deformable properties of the stimulation lead introducermay result in less trauma and reduce the possibility of causing a “wettap.” i.e., a cerebral spinal fluid (CSF) leak. A CSF leak may causesevere headaches or, if the leak is severe, neurological damage.

The details of one or more embodiments of the invention are set forth inthe accompanying drawings and the description below. Other features,objects, and advantages of the invention will be apparent from thedescription and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a diagram illustrating a stimulation lead introducing kit,which includes components for percutaneously implanting a stimulationlead.

FIG. 2 is a perspective view of a sheath and dilator useful in thestimulation lead introducing kit of FIG. 1.

FIG. 3 is a perspective diagram illustrating an exemplary dilator thatmay be used for percutaneously implanting a stimulation lead.

FIG. 4 is a perspective diagram illustrating an exemplary sheath thatmay be used for percutaneously implanting a stimulation lead.

FIG. 5 is a perspective diagram illustrating a stimulation leadintroducer, including a dilator and elongated sheath that may be usedfor percutaneously implanting a stimulation lead.

FIG. 6 is a cross-sectional diagram of a stimulation lead introducer,including a dilator and an elongated sheath that may be used forpercutaneously implanting a stimulation lead.

FIG. 7 is a cross-sectional diagram of a stimulation lead passed througha sheath.

FIG. 8 is a flow diagram illustrating an exemplary technique forpercutaneously implanting a stimulation lead by using a stimulation leadintroducer.

DETAILED DESCRIPTION

FIG. 1 is a diagram illustrating a stimulation lead introducing kit 10,which includes components for percutaneously implanting a generally flatstimulation lead. In particular, with kit 10, a generally flat, or“paddle-like,” stimulation lead may be percutaneously implanted throughthe epidural region proximate a spine of a patient. In this manner,surgical implantation procedure can be avoided. As shown in FIG. 1, kit10 includes a needle 12, a stylet 14, a guidewire 16, a dilator 18, asheath 20, and a stimulation lead 22. The elements in kit 10 are notnecessarily shown to scale in FIG. 1. The diagram of FIG. 1 depicts thedistal ends and proximal ends of the parts in kit 10 at the left andright, respectively. In general, a “distal” end will refer to the firstend of a component that is introduced into the patient, whereas the“proximal” generally extends outside of the body for manipulation bymedical personnel.

Needle 12 has a lumen that may be between approximately 14 gauge and 18gauge to allow needle 12 to receive stylet 14. In some instances, needle12 may take the form of a modified Tuohy needle, which has an openingthat is angled, e.g., approximately 45 degrees, so that an instrumentpassing through the needle exits through the needle at an angle. Stylet14 is sized to fit inside needle 12. Stylet 14 fills the lumen of needle12 to prevent coring in the tissue of a patient when needle 12 isinserted into the patient.

Guidewire 16 is an elongated, flexible instrument with a cross-sectionalwidth sized to fit within needle 12 upon withdrawal of stylet 14. Insome embodiments, guidewire 16 may have an outer diameter ofapproximately 0.050 inches to approximately 0.100 inches (1.27 mm to2.54 mm). Guidewire 16 is generally cylindrical, and may be steerable topermit deployment of the guidewire to a desired “target” site within theepidural region. In practice, guidewire 16 may be inserted throughneedle 12 and steered through the epidural region to the target site forneurostimulation therapy.

Guidewire 16 prepares a path for other medical instruments in kit 10 totraverse. In particular, guidewire 16 provides a path that is clear ofobstructions so a stimulation lead introducer, formed by dilator 18 andsheath 20, can reach the target site by advancing over guidewire 16.

Dilator 18 is an elongated, hollow structure that has a dilator proximalend and a dilator distal end. Dilator 18 defines a dilator body 26 witha dilator lumen extending between the dilator proximal end and dilatordistal end and sized to advance over guidewire 16. A substantiallyconical distal tip 28 extends from the distal end of dilator body 18.The conical tip, comprising a proximal portion 21 and distal portion 23,widens a path through the epidural region for dilator body 26 to pass.At least a portion of the dilator 18 has a substantially oblongcross-section, which allows a flat, paddle-like stimulation lead 22 tofit through the widened path.

In one embodiment, the proximal portion 21 of the conical structure 28has a substantially oblong cross-section, whereas the distal portion 23has a generally circular cross-section. An opening 24 is provided atdistal portion 23. Hence, substantially conical distal tip 28 may taperfrom an oblong cross-section at proximal portion 21 to a circularcross-section at distal portion 23, and hence a circular opening 24. Inaddition, the dilator lumen may have a substantially oblongcross-section.

Dilator 18 may be made of an extruded or molded material, e.g., apolymeric material. The material may include a substantially deformablematerial, such as polyethylene. The deformable properties of thematerial allow dilator 18 to be formed to fit the anatomy of a patientmore accurately. In some cases, a physician may be able to shape or forma portion of the dilator 18, such as distal tip 28, to a desiredconfiguration. To that end, the material in distal tip 28 may beselected to deform and hold a resulting shape. In addition, thedeformable properties of the stimulation lead introducer may reducetrauma upon passage within the epidural region and thereby decrease theprobability of causing a “wet tap”, or CSF leak, which is an event thatmay cause severe headaches or, if the leak is severe, may causeneurological damage. A CSF leak may occur if the stimulation leadintroducer is inserted too far into the epidural region, causing apuncture in the dura membrane of the epidural region. The deformableproperties of the stimulation lead introducer may allow the distal tip28 to be sufficiently soft so that it deforms enough to prevent punctureand a resulting CSF leak. In particular, distal tip 28 may bend to theside upon reaching the dura membrane, preventing a puncture in the duramembrane.

Sheath 20, an elongated, hollow structure defining an inner sheathlumen, includes a sheath proximal end and a sheath distal end. In oneembodiment, the outside of sheath 20 has a substantially oblongcross-section. In another embodiment, the sheath lumen has asubstantially oblong cross-section, whereas the outside is substantiallycircular. Thus, in some embodiments, the entire sheath 20 has an oblongcross-section, while in other embodiments, the sheath outer diameter hasa non-oblong cross-section and the inner lumen has an oblongcross-section. The term “oblong,” with respect to dilator 18 and sheath20, refers generally to a cross-section, taken normal (i.e.,perpendicular) to the longitudinal extent of the respective component,with a width that is substantially greater than its height.

Like dilator 18, sheath 20 may be made of extruded or molded material.The material may include a substantially deformable material, such aspolyethylene. The deformable properties of the material allow sheath 20to be formed to fit the anatomy of a patient more accurately. Inaddition, sheath 20 may include radio-opaque material that is viewableunder fluoroscopic imaging to aid medical personnel in visualizing thesheath during percutaneous introduction.

In practice, sheath 20 fits over dilator 18 to form the stimulation leadintroducer. In addition, sheath 20 allows for the passage of astimulation lead when dilator 16 is not present in sheath 20, i.e., uponwithdrawal of dilator 16. In one embodiment, sheath 20 may be shorterthan dilator 18 so that the conical distal tip 28 of dilator 18 extendsbeyond the distal end of sheath 20.

Stimulation lead 22 may include a paddle-shaped, flat structure with atleast one electrode 29 to provide stimulation to a patient, as shown inFIG. 1. FIG. 1 generally depicts a distal end of stimulation lead,including electrode surface 25 and lead body 27. In operation, proximalend of lead body 27 is coupled to a neurostimulator that generatesneurostimulation energy for delivery via electrodes 29. Stimulation lead22 is shown in FIG. 1 with five surface electrodes 29. In variousembodiments, the stimulation lead is a paddle lead. For example, thestimulation lead may take the form of a quad-electrode paddle lead, anoctet-electrode paddle lead, or a deployable paddle lead. A line ofneurostimulation paddle leads are commercially available from Medtronic,Inc. of Minneapolis, Minn.

FIG. 2 is a perspective view of sheath 20 and dilator 18 in stimulationlead introducing kit 10 of FIG. 1. As shown in FIG. 2, a proximal endsof sheath 20 and dilator 18 may include respective fittings 31, 33 toaccommodate insertion of dilator 18 into sheath 20. Dilator 18 may besized longer than sheath 20, so that distal tip 28 protrudes through anopening 35 in a distal portion of sheath 20.

FIG. 3 is a perspective diagram illustrating an exemplary dilator 18that may be used for percutaneously implanting a stimulation lead 22. Inparticular, dilator 18 is part of a stimulation lead introducer thatalso includes sheath 20. Dilator 18 is an elongated, hollow structurethat has a dilator proximal end and a dilator distal end. Dilator 18defines a dilator body 26 with a dilator lumen extending between thedilator proximal end and dilator distal end for advancing over guidewire16. A substantially conical distal tip 28 extends from the distal end ofdilator 18, which has an opening 24. As shown in FIG. 3, opening 24 maybe substantially circular to fit around guidewire 16. Alternatively,opening 24 may have a non-circular cross-section. For example, opening24 may have an oblong cross-section.

The conical tip 28 of dilator 18, comprising a proximal and distal end,serves to widen a path through the epidural region for the rest of thestimulation lead introducer to pass through. At least a portion ofdilator 18 may have an oblong cross-section so a flat, paddle-likestimulation lead 22 can fit in the widened path. In a furtherembodiment, the dilator lumen has a substantially oblong cross-section.As shown in FIG. 3, the proximal portion 21 of the conical tip 28,adjacent dilator body 26, may have an oblong cross-section. Also shownin FIG. 3, the body of dilator 18 has an oblong cross-section.

In one embodiment, the proximal opening may have a width ofapproximately 0.175 inches to approximately 0.195 inches (4.45 mm to4.95 mm), and the distal opening 24 may have a width of approximately0.055 inches to approximately 0.105 inches (1.27 mm to 2.67 mm). Hence,the proximal width may be greater than approximately three times thedistal width. In one embodiment, the dilator body 26 has a height thatis greater than the height of distal opening 24. The height and width ofdilator 18 may be designed to fit a particular stimulation lead that maybe passed through the path created by needle 12 and dilator 18. In oneembodiment, dilator 18 may be longer than sheath 20 so the conicalstructure 28 of dilator 18 extends past the distal end of sheath 20.

Dilator 18 may comprise extruded or molded material. The material mayinclude a deformable material such as a polymer. In particular, thepolymer may comprise polyethylene. The deformable properties of thematerial allow dilator 18 to be formed to better fit the anatomy of apatient.

FIG. 4 is a perspective diagram illustrating a distal portion of anexemplary sheath 20 that may be used for percutaneously implanting astimulation lead. Sheath 20, an elongated, hollow structure defining asheath lumen, includes a sheath proximal end and sheath distal end. Inone embodiment, the outside of sheath 20 has a substantially oblongcross-section. In another embodiment, the sheath lumen has asubstantially oblong cross-section so stimulation lead 22 can fit in thewidened path. As shown in FIG. 4, the sheath lumen may have asubstantially oblong cross-section. For example, the proximal opening 34may have a width of approximately 0.185 inches to approximately 0.205inches (4.7 mm to 5.21 mm), and a height of approximately 0.120 inchesto approximately 0.140 inches (3.05 mm to 3.56 mm). The height and widthof sheath 20 may be designed to fit a particular stimulation lead thatmay be passed through the path created by a needle 12, a guide wire 16,and a dilator 18.

Sheath 20 may comprise extruded or molded material. The material mayinclude a deformable material such as a polymer. In particular, thepolymer may comprise polyethylene. The deformable properties of thematerial allow dilator 18 to be formed to better fit the anatomy of apatient. In addition, sheath 20 may include radio-opaque material thatis viewable under fluoroscopic imaging.

In practice, sheath 20 is part of a stimulation lead introducer thatalso includes dilator 18. In one embodiment, sheath 20 may be shorterthan dilator 18. A substantially conical structure 28 on the distal endof dilator 18 may extend past the distal end of sheath 20. In addition,sheath lumen of sheath 20 allows for the passage of a stimulation leadwhen dilator 16 is not present within sheath 20.

FIG. 5 is a perspective diagram illustrating a stimulation leadintroducer 30, which may be used for percutaneously implanting astimulation lead. In particular, stimulation lead introducer 30 includeselongated sheath 20, which may fit over dilator body 26 of dilator 18.More particularly, dilator 18 may fit within a sheath lumen defined bysheath 20. Dilator 18, which comprises a dilator proximal end and adilator distal end, has a substantially conical structure 28 extendingfrom the dilator distal end. The distal end of the conical structure 28has an opening 24, which may be sized to advance over guidewire 16. Inone embodiment, dilator 18 is at least as long as sheath 20 so theconical structure 28 of dilator 18 extends through the distal end ofsheath 20.

At least a portion of the stimulation lead introducer has asubstantially oblong cross-section. As shown in FIG. 5, the proximal endof the conical structure 28 at a distal end of dilator 18 may have anoblong cross-section, while the opening 24 may have a circularcross-section. Hence, distal tip 28 is generally conical but may havedifferent cross-sectional shapes at the proximal and distal ends of thedistal tip. Also shown in FIG. 5, sheath 20 of stimulation leadintroducer 30 may have a substantially oblong cross-section. Inaddition, the sheath lumen may have a substantially oblongcross-section.

At least a portion of the stimulation lead introducer 30 may includedeformable material. In particular, sheath 20 or dilator 18 may includea deformable material such as polyethylene. The deformable properties ofthe material allow sheath 20 to be formed to fit the anatomy of apatient more accurately. In addition, at least a portion of stimulationlead introducer 30 may include a radiopaque material that is viewableunder fluoroscopic imaging. In particular, sheath 20 may include theradiopaque material.

In practice, stimulation lead introducer 30 enters the epidural regionof a patient by advancing over the guidewire 16, which prepares a pathto a target site for stimulation lead introducer 30 to follow. Animaging technique may aid the introduction of the stimulation leadintroducer 30. For example, as discussed above, fluoroscopic imaging maybe used to follow the progress of stimulation lead introducer 30 as itadvances over guidewire 16. The stimulation lead introducer 30 may widenthe path to the target site. In particular, stimulation lead introducer30 may widen the path so that the cross-section of the path issubstantially oblong.

After stimulation lead introducer 30 widens the path for stimulationlead 22 to get to the target site, dilator 18 may be withdrawn. Sheath20 remains in the epidural region, maintaining the path for theintroduction of stimulation lead 22. A stimulation lead 22 may beintroduced via sheath 20 and may be placed at the target site to deliverstimulation therapy to a patient. In particular, electrodes 29 onstimulation lead 22 may provide therapy by stimulating the target site.

FIG. 6 is a cross-sectional diagram of a stimulation lead introducer 30,including a dilator 18 and an elongated sheath 20 that may be used forpercutaneously implanting a stimulation lead. Dilator 18, which may fitinside sheath 20, has a proximal end with a greater circumference thanthat of the distal end of the dilator. The distal end of dilator 18includes opening 24, which allows dilator 18 to fit around guidewire 16.In the example of FIG. 6, the cross-section of opening 24 and thedilator proximal end may have a circular or oblong shape. In addition,the cross-section of sheath lumen may include a circular or oblong shape

As shown in FIG. 6, the proximal end of dilator 18 may have an oblongcross-section with a width 34 and a height 36. In one embodiment, width34 may be approximately 0.175 inches to approximately 0.195 inches (4.46mm to 4.95 mm) and height 36 may be approximately 0.085 inches toapproximately 0.105 inches (2.16 mm to 2.67 mm). Hence, width 34 isgreater than approximately two times height 36. In addition, the distalend of dilator 18 has a height 39, which may be approximately 0.055inches to approximately 0.105 inches (1.40 mm to 2.67 mm). In someembodiments, the cross-section of the dilator is circular. Inparticular, the width of the distal end of dilator 18 may beapproximately equal to the height 39 of the distal end of dilator 18. Asan example, the cross-section of the sheath lumen may have a width 32 ofapproximately 0.185 inches to approximately 0.205 inches (4.70 mm to5.21 mm) and a height 38 of approximately 0.120 inches to approximately0.140 inches (3.05 mm to 3.56 mm).

FIG. 7 is a cross-sectional diagram of a stimulation lead 22 passedthrough a sheath 20 following withdrawal of dilator 18. The outercross-section of sheath 20 may have a circular or oblong shape. In somecases, stimulation lead 22 may have a substantially rectangularcross-section, as shown in FIG. 7, or an oblong cross-section, providinga generally flat, paddle-like shape. The cross-section of stimulationlead 22 may have a width 43 of approximately 0.150 to approximately0.170 inches (3.81 mm to 4.32 mm) and a height 45 of approximately 0.040inches to approximately 0.055 inches (1.02 mm to 1.40 mm). In addition,the outside of sheath 20 may have a width 41 of approximately 0.205inches to approximately 0.305 inches (5.21 mm to 7.75 mm) and a height47 of approximately 0.140 inches to approximately 0.150 inches (3.56 mmto 3.81 mm).

FIG. 8 is a flow diagram illustrating an exemplary technique forpercutaneously implanting a stimulation lead by using a stimulation leadintroducer 30 as described herein. Initially, a needle assembly isinserted into the epidural region of a patient (40). The needle assemblyincludes stylet 14 fitted into a lumen defined by needle 12. The lumenmay have a diameter between 14 and 18 gauge to allow needle 12 toreceive stylet 14. Stylet 14 may fill the lumen of needle 12, preventingtissue coring. In some instances, needle 12 may include a modified Tuohyneedle, which has an opening that is angled 45 degrees so that aninstrument passing through the needle exits at an angle.

After the needle has been properly inserted into the epidural region ofa patient, stylet 14 may be withdrawn (42) from needle 12. In oneembodiment, a syringe may be used for placing the needle. If a syringeis used, the syringe is attached to needle 12 (46). Using the syringemay confirm that the needle has been properly placed into the epiduralregion. In particular, the syringe may attempt to inject fluid, such asair, into the epidural region (48). The fluid from the syringe willencounter substantial resistance if the needle is not correctly placedin the epidural region. On the other hand, a lack of substantialresistance to fluid from the syringe may indicate that the needle 12 hasbeen correctly placed in the epidural region. Once needle 12 has beencorrectly placed, the syringe may be removed.

In any event, needle 12 is placed in the epidural region, regardless ofthe presence of the syringe. Upon proper placement of needle 12, aguidewire 16 is inserted (50) into the epidural region via the lumendefined by needle 12. In particular, guidewire 16 slides through thelumen defined by needle 12. Guidewire 16 may be maneuvered through theepidural region until it reaches a target site, wherein the target siteis the location where a stimulation lead will be placed for providingstimulation therapy to the patient. In one embodiment, an imagingtechnique may aid the maneuvering of guidewire 16. For example, theimaging technique may include fluoroscopic imaging.

After the guidewire 16 has entered the body of a patient, the needle iswithdrawn (52). In one embodiment, the needle is withdrawn afterguidewire 16 has reached the target site for therapy. A small incisionmay be made (54) proximate the spine to allow entry of a stimulationlead introducer 30. A sheath 20 and a dilator 18, collectively thestimulation lead introducer 30, are inserted (56) through the incision.The dilator 18 is disposed coaxially within sheath 20. At least aportion of stimulation lead introducer 30 may have a cross-section thatis substantially oblong.

Upon insertion, stimulation lead introducer 30 is advanced overguidewire 16 until it reaches the therapy target site. As describedabove, the dilator serves to widen a path surrounding guidewire 16 so astimulation lead can fit through the path. Sheath 20 serves to maintainthe path, which may be oblong, that dilator 18 widens. Once thestimulation lead introducer 30 has reached the therapy target site,dilator 18 is withdrawn from sheath 20 (58). At this point, guidewire 16is withdrawn (60) from sheath 20, leaving a void within sheath 20. Thevoid is filled by a stimulation lead 22. Stimulation lead 22 is insertedthrough the incision (62) and advances through sheath 20 until itreaches the therapy target site. Once stimulation lead 22 reaches thetherapy target site, sheath 20 is withdrawn (64) from the epiduralregion. Electrodes 29 on stimulation lead 22 are activated (66) toprovide therapy to the patient, e.g., by coupling a proximal end ofstimulation lead 22 to a neurostimulator. In one embodiment, a leadextension may be provided to couple stimulation lead 22 to theneurostimulator.

Various embodiments of the invention have been described. These andother embodiments are within the scope of the following claims.

The invention claimed is:
 1. A stimulation lead introducer forfacilitating implantation of a lead, the stimulation lead introducercomprising: an elongated dilator defining a dilator lumen sized toadvance over a guidewire, the dilator having a substantially deformabledistal tip, wherein a distal portion of the distal tip has asubstantially circular cross-section, whereas a more proximal portion ofthe distal tip has a substantially oblong cross-section sized to widen apath through an epidural region proximate a spine of a patient byfollowing the guidewire through the epidural region proximate the spineof the patient, wherein the widened path facilitates advancement of thelead through the epidural region proximate the spine of the patient; andan elongated sheath defining a sheath lumen, wherein the sheathcomprises a sheath material that is substantially deformable, wherein atleast a portion of the sheath lumen provides a substantially oblongcross-section sized to accommodate the dilator, wherein the sheath isconfigured to facilitate advancement of the lead along a portion of thepath when the dilator is not present in the sheath, wherein the dilatoris configured to extend beyond a distal end of the sheath lumen.
 2. Thestimulation lead introducer of claim 1, wherein the dilator distal tiptapers from the substantially oblong cross-section at the more proximalportion of the distal tip to the substantially circular cross-section atthe distal portion of the distal tip.
 3. The stimulation lead introducerof claim 1, wherein an outer surface of the sheath has a substantiallyoblong cross-section with a width of the cross-section of the sheaththat is greater than approximately two times a height of thecross-section of the sheath.
 4. The stimulation lead introducer of claim1, wherein the sheath material is substantially elastically deformable.5. The stimulation lead introducer of claim 1, wherein the distal tip isselectably deformable to hold a shape.
 6. The stimulation leadintroducer of claim 1, wherein a distal opening to the dilator lumen issubstantially circular to fit around the guidewire.
 7. The stimulationlead introducer of claim 1, wherein a width of an outside of the sheathis within a range from approximately 5.21 millimeters to approximately7.75 millimeters, and a height of the outside of the sheath is within arange from approximately 3.05 millimeters to approximately 3.56millimeters.
 8. The stimulation lead introducer of claim 1, wherein thedeformable properties of the distal tip of the dilator decrease theprobability of causing a cerebral spinal fluid leak from a puncture in adura membrane as the dilator widens the path through the epidural regionproximate the spine of the patient.
 9. The stimulation lead introducerof claim 1, wherein the sheath is configured to maintain the path in theepidural region for advancement of the stimulation lead to a target sitevia the sheath after withdrawal of the dilator from the sheath lumen.10. A method for introducing a stimulation lead comprising: inserting aneedle into an epidural region proximate a spine of a patient; insertinga guidewire into the needle such that a distal end of the guidewireextends within the epidural region proximate the spine of the patient;withdrawing the needle over the guidewire from the epidural region ofthe patient; inserting a stimulation lead introducer to a target sitewithin the epidural region proximate the spine of the patient via theguidewire following withdrawal of the needle, the stimulation leadintroducer widening a path created by the needle to have a substantiallyoblong cross-section, wherein the introducer includes: an elongateddilator defining a dilator lumen sized to advance over a guidewire, thedilator having a substantially deformable distal tip, wherein a distalportion of the distal tip has a substantially circular cross-section,whereas a more proximal portion of the distal tip has a substantiallyoblong cross-section sized to widen a path through an epidural regionproximate a spine of a patient by following the guidewire through theepidural region proximate the spine of the patient, wherein the widenedpath facilitates advancement of the lead through the epidural regionproximate the spine of the patient; and an elongated sheath defining asheath lumen, wherein the sheath comprises a sheath material that issubstantially deformable, wherein at least a portion of the sheath lumenprovides a substantially oblong cross-section sized to accommodate thedilator, wherein the sheath is configured to facilitate advancement ofthe lead along a portion of the path when the dilator is not present inthe sheath; withdrawing the guidewire from the epidural region proximatethe spine of the patient; withdrawing the dilator from the sheath; andintroducing the stimulation lead within the epidural region proximatethe spine of the patient via the sheath following withdrawal of thedilator and the guidewire.
 11. The method of claim 10, furthercomprising attaching a syringe to the needle, prior to inserting theguidewire into the needle, and attempting to inject fluid into theepidural region proximate the spine of the patient via the syringe andthe needle to evaluate a position of the needle.
 12. The method of claim10, further comprising activating the stimulation lead to stimulate anerve after introducing the stimulation lead within the epidural regionproximate the spine of the patient.
 13. The method of claim 10, whereinthe dilator distal tip tapers from the substantially oblongcross-section at the more proximal portion of the distal tip to thesubstantially circular cross-section at the distal portion of the distaltip.
 14. The method of claim 10, wherein an outer surface of the sheathhas a substantially oblong cross-section with a width of thecross-section of the sheath that is greater than approximately two timesa height of the cross-section of the sheath.
 15. The method of claim 10,wherein the distal tip is selectably deformable to hold a shape.
 16. Themethod of claim 10, wherein a width of an outside of the sheath iswithin a range from approximately 5.21 millimeters to approximately 7.75millimeters, and a height of the outside of the sheath is within a rangefrom approximately 3.05 millimeters to approximately 3.56 millimeters.17. A kit for implanting a lead proximate a spine of a patient via apath through the epidural region proximate the spine, the kitcomprising: a needle configured for insertion into the epidural regionproximate the spine of the patient; a guidewire sized to pass through alumen of the needle and into the epidural region proximate the spine ofthe patient; and a stimulation lead introducer, wherein the stimulationlead introducer includes: an elongated dilator defining a dilator lumensized to advance over the guidewire, the dilator having a substantiallydeformable distal tip, wherein a distal portion of the distal tip has asubstantially circular cross-section, whereas a more proximal portion ofthe distal tip has a substantially oblong cross-section sized to widen apath through an epidural region proximate a spine of a patient byfollowing the guidewire through the epidural region proximate the spineof the patient, wherein the widened path facilitates advancement of thelead through the epidural region proximate the spine of the patient; andan elongated sheath defining a sheath lumen, wherein the sheathcomprises a sheath material that is substantially deformable, wherein atleast a portion of the sheath lumen provides a substantially oblongcross-section sized to accommodate the dilator, wherein the sheath isconfigured to facilitate advancement of the lead along a portion of thepath when the dilator is not present in the sheath.
 18. The kit of claim17, wherein the needle is a Tuohy needle.
 19. The kit of claim 17,further comprising a stylet sized to fit inside the needle lumen toprevent coring of tissue when the needle is inserted into a patient. 20.The kit of claim 17, wherein the dilator distal tip tapers from thesubstantially oblong cross-section at the more proximal portion of thedistal tip to the substantially circular cross-section at the distalportion of the distal tip.